1. Field of the Invention
The present invention relates generally to the field of respiratory masks.
2. Description of the Background Art
A respiratory mask is a device used to deliver a gas or gases to a person. FIG. 1 shows a respiratory mask 100 of the related art. The respiratory mask 100 includes a mask shell 104, a gas supply hose 107, a vent aperture 112, and an optional gasket 115. The mask shell 104 is fitted over a face of the person in order to supply a gas to a respiratory system of the person.
The respiratory mask 100 may be used to deliver any variety of gases, including air or oxygen, and a variety of medicines or treatments. Preferably, the mask shell does not allow a supplied gas to escape. A strap or other attaching means may be affixed to the mask shell and may be fitted over the head of the person. Constant pressure gas is therefore delivered, with the vent aperture 112 maintaining a substantially constant pressure in the mask. This is referred to as a continuous positive airway pressure (CPAP) mask. The vent aperture 112 allows expired carbon dioxide to escape from the mask. It is important that the vent aperture 112 be of a sufficient size to exhaust substantially all expired carbon dioxide under normal conditions of use.
In the related art, the need for venting has meant simply an aperture on or close to the mask shell, whereby exhaled air is flushed out of the respiratory mask by the positive pressure generated by the gas supply hose. This is taught by Rapaport U.S. Pat. No. Re. 35,339.
Several drawbacks exist with the venting of the related art respiratory mask 100. First, the air circulation within the mask 100 and vent aperture 112 may create annoying noises. Second, a jet of air from the vent aperture 112 may impinge on the wearer or on nearby persons. This can be seen in FIG. 1, where the vent aperture 112 and a resulting air jet are relatively close to the face of the wearer, and will in all likelihood be in the region of persons near to or sleeping with the wearer. As a result, these drawbacks may affect compliance with a therapy.
Therefore, there remains a need in the art for an improved respiratory mask.
A respiratory mask having a variable flow venting is provided according to the invention, comprising a gas supply hose, a mask shell adapted to output a gas to a respiratory system of a person, the mask shell adapted to be connected to the gas supply hose, and a gas flow volume regulating device which maintains a substantially constant gas flow volume out of the respiratory mask independent of an internal gas pressure inside the respiratory mask.
The above and other features and advantages of the present invention will be further understood from the following description of the preferred embodiment thereof, taken in conjunction with the accompanying drawings.